Nat. Med. 18, 1503–1510 (2012); published online 16 September 2012; corrected after print 20 November 2012

In the version of this article initially published, the formula to calculate the mutual information matrix, which appears in the last page of the Online Methods, was missing a log multiplier. The correct formula is below, and the error has been corrected in the HTML and PDF versions of the article.